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EC fan potentiometers and control switches

EC fans, AC fan speed controllers or damper actuators are often controlled via a 0-10 Volt analogue control signal. Control signals are typically used to control devices remotely. Such control signal can be generated manually via a potentiometer or control switch. Via the potentiometer, fan speed can be set remotely.
EC fan potentiometers and control switches

0-10 Volt potentiometer
Analogue control signals have been popular in the (home) automation industry for many years. Via a simple 0-10 Volt signal, the desired fan speed is transmitted to the EC fan or AC fan speed controller. The 0-10 Volt control signal can be manually generated via a potentiometer (infinitely variable) or via a control switch (in steps). It is a simple technology that works fine if cable lengths remain limited. However, if the control lines are installed nearby power lines, there is a risk of interferences. It is advisable to keep the cable length of the analogue control signal limited to maximum 50 m and to use shielded cables to minimise the risk of interferences.

Control switch for 3-step fan speed control
The SMT-D series of control switches are often used to adjust fan speed in 3 steps. Control switches generate a 0-10 Volt signal in 3 steps. They are available with or without OFF position. Their stepped 0-10V signal can be used to control EC fan, AC fan speed controllers, frequency inverters, etc. Position 1 and position 2 can be adjusted via internal trimmers. Position 3 is equal to the supplied voltage – typical 10 VDC. In case there is an off position, this corresponds to 0 VDC.

Potentiometers for variable fan speed control
A potentiometer allows you to manually generate an infinitely variable control signal - for example 0-10 Volt. The 0-10 Volt control signal is often used for infinitely variable EC fan speed control. It can also control a frequency inverter, an AC fan speed controller, etc. Some potentiometers generate other analogue control signals, e.g. 0-20 mA or a PWM signal. Potentiometers are available with different supply voltages, with or without off position, etc.

Potentiometer with Modbus RTU communication
SPV series are potentiometers with Modbus RTU communication on board. Digital communication (e.g. Modbus RTU communication) offers many advantages. Cable lengths up to 1.000 m are possible. Multiple values can be transmitted in both ways. Not only the desired fan speed can be sent to the motor, also the potentiometer position is available remotely. The potentiometer status can be read out via the Modbus master device or – if connected to SenteraWeb via an internet gateway – remotely via the internet. The potentiometer output value can be set locally or it can be overruled via Modbus RTU communication. This makes it possible to switch the ventilation system in the complete building to high level during a certain period of time by overruling the output values temporarily.

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